1. Field of the Invention
The present invention relates to a code division multiple access (CDMA) base station system, and more particularly to a CDMA base station system which reduces the deterioration of call quality.
2. Background of the Related Art
FIG. 1 is a block diagram illustrating the construction of a related art CDMA base station system.
Referring to FIG. 1, the related art CDMA base station includes a base station processor 101 for taking charge of an interface in a base station and controlling peripheral boards. It further includes an upper processor 102 for taking charge of an interface between the base station and an exchange (not illustrated). The upper processor 102 is communicatively coupled to base station processor 101. Next, a channel card 103 is provided to modulate/demodulate signals transmitted/received from the base station.
The CDMA base station also includes a transmitted frequency converter 104 to convert a transmitted frequency into an allocated use frequency band, and a transmitted power amplifier 106 to amplify the signal to transmit at a rated power of the base station. A transmitted frequency band filter 108 is provided to allow only the allocated frequency band (i.e., the transmitted frequency band to be used) to pass through to the transmitting antenna 111.
The CDMA base station next includes a received frequency converter 105, to convert a received frequency into a frequency band used in the base station. A receiving amplifier 107 is coupled to the frequency converter 105 for amplifying a low-level signal from a terminal, and a received frequency band filter 109 is coupled to the receiving amplifier 107, and allows only the allocated frequency band to pass through. Finally, a power level measuring device 110 is provided to measure a power level of a final end (i.e., an output) of the base station.
An operation of the related art CDMA base station system as constructed above will now be described with reference to FIG. 1.
The operation of the related art CDMA base station is typically divided into three functions: (1) base station transmission; (2) base station reception; and (3) output signal strength detection.
First, during the transmitting function of the base station, the channel card 103, which controls the transmitted/received signal modulation and demodulation, modulates the transmitted signal of the CDMA base station. The modulated signal then passes through the transmitted frequency band filter 108 via the transmitted frequency converter 104. This is done to convert the transmitted signal into the frequency to be actually used (i.e., allocated use frequency). Next, after passing through the transmitted frequency converter 104, the signal passes through the transmitted power amplifier 106 to increase the transmission power to the rated power (i.e., the maximum power of the base station that can be transmitted within the range satisfying the characteristic of the base station).
The signal is then outputted from transmitted power amplifier 106 and passes through the transmitted frequency band filter 108, and then transmitted through the transmission antenna 111.
The receiving function of the CDMA base station is contrary to the transmission function. A signal is first received through a receiving antenna 112, and then passes through the received frequency filter 109. The filter 109 is used to ensure that only the allocated frequency band is outputted from the received frequency band filter 109. The signal, having passed through the received frequency band filter 109, is then amplified by the receiving amplifier 107 as much as the power of the received signal required by the CDMA base station. The thusly amplified signal is then is converted into a low frequency signal required by the CDMA base station through the received frequency converter 105.
The low frequency signal is then demodulated by the channel card 103 in charge of the transmitted/received signal modulation and demodulation.
Finally, the CDMA base station measures the strength of the current transmitted signal of the final end using the power level measuring device 110. The power level measuring device 110 detects the strength of the transmitted output, and reports the measured strength to the base station processor 101.
The related art CDMA base station has various problems. For example, according to the related art CDMA base station, the processor 101 simply confirms whether or not the power supply to the boards of the channel card 103, transmitted/received frequency converters 104 and 105, transmitted/received power amplifiers 106 and 107, transmitted/received frequency filters 108 and 109, etc., is in a normal state, or whether the cables connected among them are in a normal state.
The actual call quality, however, can be affected by the board operation characteristics other than the power supply to the boards. Despite this, no method of confirming the board characteristics beyond checking the power supply to the boards has been conventionally proposed.
As a result, the related art CDMA base station has no way to confirm the RF characteristics of the base station. Consequently, except for the reading of the final received power level, the RF characteristic of the base station cannot be recognized until a problem occurs and affects the call quality.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.